1985 ZN700 transmission rebuild

Hey again all,
After 33k miles and 3 sets of hands (a dead guy, my buddy and now me), my 1985 ZN700 Shaft’s 2nd gear has absolutely had it. It slips out of gear and grinds into gear (if you can catch 2nd at all), especially when upshifting. The oil did not come out sparkly, so I imagine alot of the teeth in there are broken.

In sum, it needs to be gone thru badly.

What should I look for in terms of parts and gaskets? Can I swap in a transmission that doesn’t do 5500k rpm at 70? Are there mechanic’s manuals that tell me how to help the transmission? I see there are whole used transmissions on EBay for ~60$.

I want to help this bike, but I have never done this before and I don’t know what I’m doing. I have done top end work, but never as deep as a transmission.

Any help is obliged.
Chris

Have found a transmission, just don’t know how to swap it in. 

You need to split the cases, probably best to study the manual before you start. There should be no need to disturb the top end

Have been doing so since this thread is pretty untouched. I had to find a certain KZ750 Shaft service manual that covered my ‘85 ZN700.

May have to touch top end anyways since the cam chain tensioner is getting there.

My suggestion is to find a motorcycle mechanic who has experience and the proper tools to work on these bikes. 

Sure, and I do know decent people who handle these old bikes, but it’d cost me an arm and a leg to have them, qualified and trustworthy, actually fix it.

My ZN700 is worth less than what it’d cost to do that. I have some experience working on internal engine components, so it shouldn’t be too unfamiliar for me.

I just need to find a master gasket kit.



 

I suggest you have somebody with experience carefully check the new transmission before installing it. What usually goes bad are the shift dogs, not the teeth on the gears. The more rounded the dogs get, the less able the gears are to stay engaged. 
All of the transmission gears are always engaged with their partner on the other shaft. The dogs and slots on the sides of the gears determine which pair of gears are transmitting power at any given moment.

Yes, it is possible to explode a gear with enough abuse, and it more often than not will be second gear. However, a transmission that at first glance looks ok may have dogs so badly worn that it cannot stay in any gear.

An inspection may save you another tear down.

P.S. The best gaskets available are from Kawasaki, though the company does not sell kits. If you decide to go aftermarket, stay away from Athena. Their green base gaskets have a reputation for turning into a gooey, leaky mess.

Thanks for the heads up, I was just about to buy a set from them. I’ll have to see what I can gather from Kawasaki with some old part numbers.

As for the dogs, anything would be better than what I have at this point. The ZN stopped going into 2nd gear at all. I’m draining the oil out of it this weekend and I’m guessing I will find whatever was left of 2nd gear in there. 

The gearbox has ~15k miles on it and looks pretty much brand new. There is zero rounding on the edges of the dogs and the inner catches on 1st and 3rd look fine.

I will listen though, since I have time I’ll go say hi to some of my friends at Retrospeed here in Wisconsin to have a look at it.

Thanks alot,
Chris